Estimated to make up more than half of all animal life, only about 10 percent of insect species are thought to have even been named. “That’s where the hobbyists from Krefeld come in.”Their study looks at 63 nature preserves mostly in the area around Krefeld. But experts say it is likely to reflect the insect situation in places like North America, where monoculture and pesticide use are widespread. Advertisement Continue reading the main storyCalling the Krefelders’ data “a rich treasure trove,” Mr. Tscharntke warned that entomology hobbyists are themselves a dying species. “In a lot of places, everything gets thrown out — the papers, the insect collection,” said Martin Sorg, a longstanding member of the Krefeld society whose expertise includes wasps.